Dolby Digital vs. Dolby E
Dolby Digital is designed for transmission to consumers. It has high bandwidth efficiency and is not optimized for multiple encode/decode cycles or editing. Dolby E allows programs to be decoded, processed and re-encoded many times without degradation as the signal makes its way through the broadcast distribution chain. Audio and video frame rates are the same with Dolby E, enabling precise video picture edits without mutes or glitches.
Broadcasters use Dolby E to get the audio to the transmitter, and Dolby Digital to get the audio from the transmitter to consumers. Dolby E is a digital audio compression technology designed for use by TV broadcast and production professionals in and among their facilities. It allows an AES/EBU (Audio Engineering Society/European Broadcasting Union) audio pair to carry up to eight channels of digital audio and Dolby Digital metadata. Audio can be edited without mutes or clicks and can be encoded and decoded multiple times without audible degradation.